This invention relates to a display device, and more particularly to a compact edge-illuminated projection display based on switchable Bragg gratings.
There is growing consumer demand for projection displays that can be built into mobile devices such as mobile telephones and hand-held computers. However, image sizes and resolutions required for typical applications such as internet browsing or viewing high definition films are already beyond the scope of display technologies currently available for use in mobile devices. New ultra compact projectors known as picoprojectors provide one solution to this problem. Many of the picoprojector designs considered to date rely on conventional flat panel display technologies such as Liquid Crystal Display (LCD) or Digital Light Processor (DLP) technology such as that developed by Texas Instruments (TX). Optical design limits the miniaturization possible with either approach, even when solid state lasers are used as the light source. An alternative approach is to scan the image using micro-optical-electrical-mechanical systems (MOEMS), essentially writing the image using a flying spot. Although MOEMS are much smaller than LCDs or DLPs they present complex opto-mechanical design problems. Very high scanning speeds, resolutions and the tight synchronization of mirror driver and laser modulation are needed in order to deliver high resolution images. Achieving the mechanical robustness required in portable applications is also a challenge. A further problem is that it is also difficult to correct laser speckle in scanned displays.
Desirably, display technologies for portable devices should be very compact with volumes of a few cubic centimeters. A thin form-factor is desirable for ease of integration into devices such as mobile telephones.
There is a requirement for a compact solid-state high-resolution data projection display with a thin form factor.